WHEN does an interstellar gas cloud look like honeycomb? When the debris thrown up by two exploding stars collides, suggests a new analysis of the mysterious Honeycomb Nebula (pictured).

Since it was first discovered in 1992, the curious shape of the Honeycomb Nebula, which lurks in a nearby galaxy called the Large Magellanic Cloud, has been a puzzle.

As it floats in an area of the LMC racked by the explosions of numerous supernovae in recent cosmic history, one theory was that the pattern might be caused by a set of localised ripples created when clumps of debris from an ancient supernova were hit by a blast wave from a relatively recent one.

This theory now has support. John Meaburn of the University of Manchester, UK, and his colleagues analysed the light spectrum of the Honeycomb Nebula and found that it resembles the spectrum produced by fast-moving gas in other supernova remnants. Their results will appear in Monthly Notices of the Royal Astronomical Society.

The case isn't closed: the honeycomb could be the result of a high-speed jet from a black hole slamming into surrounding gas. However, the team says the nebula's light spectrum is different to that of a black hole jet seen in a binary system called SS 433.